Ancient Carbon Released From Congo Lakes, Study Finds
The Congo Basin, a vast area of approximately 3 million square kilometers in Central Africa, is intersected by the Congo River and its tributaries. The region contains some of Africa’s largest rainforests – second in size globally only to the Amazon – as well as swamp forests and extensive wetlands.
Researchers at the Swiss Federal Institute of Technology in Zurich (ETHZ) have discovered that large lakes within the central peatlands of the Congo Basin are releasing millennia-old carbon into the atmosphere as CO2. This finding has implications for understanding carbon cycling and climate change in tropical regions.
Mai-Ndombe and Tumba Lakes Emit Ancient Carbon
The phenomenon is particularly noticeable in the large lakes Mai-Ndombe and Tumba. Lake Mai-Ndombe’s waters have a dark tea-like color, surrounded by extensive swamp forests and lowland rainforests growing on a thick layer of peat. The dark brown color of the water results from the leaching of organic matter from the surrounding peatlands and forests. Mai-Ndombe is the largest lake of this type in the Congo Basin.
The discovery, detailed in “Nature Geoscience,” is surprising because it was previously believed that the carbon stored in the peat was stably sequestered for a very long time. Researchers now estimate that up to 40% of the carbon released from the lakes in the Congo Basin originates from peat that accumulated in the surrounding ecosystems over thousands of years.
“You could say there’s a leak in the carbon reservoir, releasing old carbon,” said Matti Barthel, a research associate in the Sustainable Agroecosystem (SAE) research group.
Tropical Carbon Store Stability
Although the peatlands of the Congo Basin cover only 0.3% of the Earth’s land surface, they store one-third of the carbon found in all tropical peatlands. The area is difficult to access, making thorough investigation challenging. The exact mechanisms by which carbon is released from the peat into the lakes, and subsequently as CO₂ into the atmosphere, remain unclear. Researchers are now focused on determining whether the release of old carbon represents a destabilizing tipping point or a natural state balanced by new peat deposits. Is this a chain reaction triggered by climate change, deforestation, or other factors?
Researchers emphasize that identifying these emissions from the lakes changes the understanding of the stability of tropical carbon stores.
“Our findings help to refine global climate models, as tropical lakes and wetlands have been insufficiently considered in them so far,” said Johan Six of ETH, head of the SAE research group.
